A significant body of scientific and clinical evidence supports atherectomy as a viable primary or adjunctive therapy prior to stenting for the treatment of occlusive arterial disease.
Atherectomy offers a simple mechanical advantage over alternative therapies. By removing the majority of plaque mass (debulking), it creates a larger initial lumen and dramatically increases the compliance of the arterial wall. As a result, stent deployment is greatly enhanced.
Additionally, atherectomy provides several advantages related to the arterial healing response. When circumferential radial forces are applied to the vasculature, as in the case of angioplasty or stenting, the plaque mass is displaced, forcing the vessel wall to stretch dramatically. This stretch injury is a known stimulus for the cellular in-growth that leads to restenosis. By using atherectomy to remove the disease with minimal force applied to the vessel, large gains in lumen size can be created with decreased vessel wall injury and limited elastic recoiling. These effects have been shown to generate better acute results and lower restenosis rates.
Despite its advantages, atherectomy is not commonly performed due to the cost, complexity and limited applicability of available atherectomy devices. Many designs are unable to treat the wide range of disease states present in long complex lesions; luminal gain is often limited by the requirement of the physician to introduce multiple devices with increased crossing profiles; tissue collection is either unpredictable or considered unnecessary based on assumptions regarding small particle size and volumes; and optimal debulking is either not possible due to a lack of intravascular visualization or requires very long procedure times. Based on these limitations, current devices are likely to perform poorly in the coronary vasculature where safety and efficacy in de novo lesions, ostials, and bifurcations continue to pose great challenges.
In the past, atherectomy devices have focused on macerating or emulsifying the atherosclerotic plaque such that either it might be considered clinically insignificant enough to remain in the blood stream or that it can be aspirated proximally through small spaces in the catheter main body. When the plaque is not aspirated through the catheter to an external reservoir, the reliability of these devices to produce clinically insignificant embolization has been challenged. Aspiration necessitates that a vacuum be applied to a lumen or annular space within the catheter to remove emulsified tissue. In early clinical evaluations of aspiration, the presence of negative pressure at the distal working assembly caused the artery to collapse around the cutting element. This effect results in more aggressive treatment, dissections and/or perforations. In addition, options for post-procedural analysis of any removed disease are extremely limited or impossible using this methodology.
Other atherectomy devices include directional atherectomy devices, which use cup-shaped cutters that cut and “turn” the tissue distally into a storage reservoir in the distal tip of the device. This approach preserves the “as cut” nature of the plaque, but requires large distal collection elements. These large distal tip assemblies can limit the capability of the system to access small lesions and may cause additional trauma to the vessel.
Currently available atherectomy devices also do not include, and are poorly adapted for use with, real time image guidance. Although intravascular diagnostic devices have consistently shown lesions that are significantly eccentric, the typical practice of physicians is to treat target lesions as if they contain concentric disease. This circumferential treatment approach virtually ensures that potentially native arterial wall and healthy vessel will be cut from the vasculature.
Further, several design challenges are presented by a single use, disposable, and single-direction imaging catheter, such as an atherectomy catheter. For example, obtaining a clear image can be difficult, as nonuniform rotational distortion (“NURD”) can occur in the image as a result of the cutter vibrating or stalling as it encounters different types of tissue. Moreover, the imaging fiber, which runs from the static light source to the rotating distal tip, can become wound up as the catheter is in active (cutting) mode. Further, a motor can be required to drive the imaging assembly at the appropriate revolution rates for imaging, thereby significantly increasing the cost and complexity of the catheter.
Atherectomy catheter devices, systems and methods that may address some of these concerns are described and illustrated below.
SUMMARY OF THE DISCLOSURE
Described herein are atherectomy catheters with on-board imaging, systems including the atherectomy catheters, and methods of using the atherectomy catheters and systems.
In general, in one embodiment, an atherectomy catheter includes an elongate flexible catheter body, a cutter near the distal end of the catheter body, a drive shaft connected to the cutter and extending within the catheter body, an imaging element near the distal end of the catheter body and an imaging shaft connected to the imaging element and extending within the catheter body. The cutter and the imaging element are mechanically isolated, and the drive shaft is configured to be axially translated relative to the imaging shaft and the catheter body.
This and other embodiments can include one or more of the following features. The drive shaft and imaging shaft can be decoupled along the length of the catheter body. The drive shaft and imaging shaft can be coupled at a proximal end of the device. The atherectomy catheter can include a handle configured to transmit torque simultaneously to the proximal end of the drive shaft and the imaging shaft, and the drive shaft and imaging shaft can be coupled within the handle. The handle can include a translation mechanism configured to translate the drive shaft without translating the imaging shaft. The atherectomy catheter can include an inflatable element configured to urge the cutter against a vessel wall. The atherectomy catheter can include an elongate distal tip connected to the catheter body, and the elongate distal tip can include a cutting window therein, the cutting window sized and dimensioned so as to cause tissue to invaginate within the cutting window. The imaging element can include an optical fiber, and the optical fiber can be coupled to the imaging shaft only at a distal end of the imaging shaft. The imaging element can include an optical coherence tomography imaging element. The drive shaft and imaging shaft can be concentric, and the drive shaft can extend within the imaging shaft. The drive shaft and the imaging shaft both can extend substantially along a central axis of the catheter body. The imaging element can include an optical fiber, and the optical fiber can extend off-axis along the length of the catheter body. The optical fiber can be configured to rotate within the imaging shaft without wrapping around the drive shaft. The drive shaft and imaging shaft can be parallel. The imaging shaft can extend off-axis relative to the elongate body. The drive shaft can extend on-axis relative to the elongate body. The atherectomy catheter can include a handle configured to transmit torque simultaneously to the proximal end of the drive shaft and the imaging shaft. The handle further can include a rotation knob configured to allow rotation of the elongate body up to three rotations. The knob can include a rotation limiter, the rotation limiter can be configured to allow rotation of up to a set amount between one and three rotations while not lengthening the elongate body. The drive shaft and imaging shaft can be concentric, and the imaging shaft can extend within the drive shaft. A distal end of the drive shaft can include a clear annular portion connected to the cutter. The imaging element can be configured to be axially aligned with the clear annular portion for imaging. The clear annular portion can include sapphire, polycarbonate, glass, or acrylic.
In general, in one embodiment, an atherectomy catheter includes an elongate flexible catheter body. The atherectomy catheter includes a drive shaft extending within the catheter body, the drive shaft having a cutter attached thereto. The atherectomy catheter includes an elongate distal tip connected to the catheter body at a hinge point. The atherectomy catheter includes an inflatable body linked to the elongate flexible catheter body and to the elongate distal tip such that inflation of the inflatable body axially deflects the elongate distal tip away from the elongate flexible catheter body at the hinge point to expose the cutter. The inflatable body is linked to the elongated flexible catheter body and the elongated distal tip with a sling extending along an outer surface of the balloon and attached to the elongated flexible catheter body and the elongate distal tip.
This and other embodiments can include one or more of the following features. The atherectomy catheter can include a biasing mechanism configured to return the elongate distal tip to a position approximately axially aligned with the catheter body. The biasing mechanism can include a wedge activated by placing axial force on the drive shaft. The elongate distal tip can include a cutting window therein, and the cutting window can have an asymmetric shape configured to prevent the cutter from hitting a distal edge of the cutting window. The atherectomy catheter can include an imaging element attached to the cutter and configured to rotate therewith. The imaging element can be an optical coherence tomography imaging element. The imaging element can include an optical fiber, and the optical fiber can extend through the drive shaft substantially on-axis with the catheter body.
In general, in one embodiment, an atherectomy assembly includes an elongate flexible catheter body. The atherectomy assembly includes a drive shaft extending within the catheter body. The drive shaft has a rotatable cutter attached thereto and is axially movable with respect to the elongate flexible catheter body. The atherectomy assembly includes an optical fiber attached to the cutter and configured to rotate therewith. The atherectomy assembly includes a handle having a distal end attached to the elongate body and a proximal end configured to connect the optical fiber to a light source. The handle is configured such the optical fiber is axially movable with respect to the distal end and axially fixed with respect to the proximal end.
This and other embodiments can include one or more of the following features. The handle can include a tube within which the optical fiber can reside. The optical fiber can be configured to wind within the tube. The tube can be shaped as a ring, and the optical fiber can be configured to conform to an outer perimeter of the tube when in a compressed configuration and to conform to an inner perimeter of the tube when in an extended configuration. The optical fiber can be configured to transmit an optical coherence tomography signal.